Persistent sore throat lasting months

Question

Expert avatarFamily Physician, Doctor2,592 Satisfied customersHello. Ive been suffering from a sore throat for about 4 months now. It started when I began taking corticosteroids for my weed allergies. I took them before without issues. A crater shaped white ulcer began forming on my right tonsil and it had white puss exudate. I visited a doctor that sent me to a throat and nose doctor. He said it's not cancer and that Im completely healthy. Still, my sore throat has only gotten worse and the ulcer spread, also forming on my left tonsil. A dentist prescribed me sumamed for Plaut-Vincent's angina, I took it for 6 days and after a week after the last pill, while the ulcers look less bulky, the pain is the same or worse. I'm getting desperate for answers and it's seriously negatively impacting my quality of life. What could the problem be?